Bacitracin

Spectrum of activity and susceptibility data

Bacitracin is a narrow-spectrum antibiotic. It targets gram-positive bacteria, especially those that cause skin infections. The following represents susceptibility data for a few medically significant microorganisms.^[10]

• Staphylococcus aureus – ≤0.03 μg/mL – 700 μg/mL
• Staphylococcus epidermidis – 0.25 μg/mL – >16 μg/mL
• Streptococcus pyogenes – 0.5 μg/mL – >16 μg/mL

Mechanism of action

Bacitracin interferes with the dephosphorylation of C₅₅-isoprenyl pyrophosphate, and a related molecule known as bactoprenol pyrophosphate; both of these lipids function as membrane carrier molecules that transport the building-blocks of the peptidoglycan bacterial cell wall outside of the inner membrane.^[11]

History

Bacitracin was isolated by Balbina Johnson, a bacteriologist at the Columbia University College of Physicians and Surgeons.^[12] Its name derives from the fact that a compound produced by a microbe in young Margaret Tracy's (1936–1994)^[13] leg injury showed antibacterial activity.^[14]

One strain isolated from tissue debrided from a compound fracture of the tibia was particularly active. We named this growth-antagonistic strain for the patient, "Tracy I." When cell-free filtrates of broth cultures of this bacillus proved to possess strong antibiotic activity and to be non-toxic, further study seemed warranted. We have called this active principle "Bacitracin.^[12]

Bacitracin was approved by the US FDA in 1948.^[15]

Synthesis

Bacitracin is synthesised via

Bacitracin is composed of a mixture of related compounds with varying degrees of antibacterial activity. Notable fractions include bacitracin A, A1, B, B1, B2, C, D, E, F, G, and X.[17] Bacitracin A has been found to have the most antibacterial activity. Bacitracin B1 and B2 have similar potencies and are approximately 90% as active as bacitracin A.^[18]

Society and culture

Controversies

Claims that bacitracin is a